The present invention relates to the field of self-tracking rollers or idlers for use in conjunction with dual or sandwich belt endless conveyor systems. More particularly, this invention relates to a new and improved self-tracking impact absorbing sandwich belt roller comprised of two groups of alternating idler rings and spacer rings having a variable sized space therebetween.
Dual endless conveyor belts, commonly termed sandwich belts, are well known to those skilled in the art. These dual belt systems typically comprise two endless conveyor belts which are urged into a sandwich-like contact therebetween and have been found aptly suited for transporting sludge, filter cake, solid or semi-solid bulk material, sewage and other slurry type materials. Prior art dual belt systems of this type are disclosed in U.S. Pat. No. 3,910,405.
Unfortunately, sandwich conveyor belt systems suffer from assorted tracking and guidance problems which may cause detrimental effects, the most important being product spillage with subsequent cots of clean-up, downtime for repair and potential damage to the belts themselves. Numerous attempts have been made to improve belt tracking for dual endless conveyor belts, such as, for example, the mutually interlocking belt system described in U.S. Pat. No. 2,836,285. These interlocking belts, however, are difficult and often prohibitively expensive to manufacture.
Other attempts at improving the tracking of dual or sandwich belts have included complex and complicated guidance systems. But, as with the interlocking belts, the guidance systems are very expensive to manufacture and install and are often of questionable efficiency. Consequently, the complicated nature and high cost of these guidance systems pose serious drawbacks and deficiencies.
Many of the tracking problems of dual conveyor belts are a result of the particular rollers currently in use. These rollers typically utilize either flat or impact ring-type rollers. Solid idler-type rollers comprised of a suitable metal material are also commonly found. Unfortunately, both types of idlers necessitate the undesirable and complicated guidance systems discussed above.
A number of rollers for use in conjunction with single belt conveyor systems and having a degree of automatic centering or self-tracking capability have been disclosed in, for example, U.S. Pat. Nos. 2,592,581, 2,772,879, 3,029,655, 3,219,176 and 3,248,775. While these self-centering rollers are suitable for certain single belt conveyor applications, the rollers described in the referenced patents are not suited for use in dual or sandwich belt systems wherein sludge or similar material is to be elevated and/or conveyed.
It would be advantageous therefore to provide a low-cost self-tracking roller for use in conjunction with sandwich type conveyor belt systems so that problems relating to tracking and centering may be efficiently reduced or overcome.